In U.S. Pat. No. 5,169,441, Lauzon suggests the use of Zeta Potential for characterizing particulates such as pigments treated with cationic polymers. Lauzon's U.S. Pat. No. 5,846,308 describes the stabilization of a rosin dispersion for use as a sizing composition by treating it with a “cationic colloidal coacervate” which may include both a cationic polymer and an anionic surfactant; the finished sizing composition is to have a Zeta Potential of at least 20 millivolts. Poly(diallyldimethyl ammonium chloride), sometimes known as polyDADMAC, is the preferred cationic polymer. Also, Lauzon's U.S. Pat. No. 6,315,824 describes a similar coacervate stabilizing system used for hydrophobic non-rosin sizing agents, which may be liquid as well as solid. See also Lauzon's U.S. Pat. No. 4,507,210, which suggests a correlation of Zeta Potential to certain filtration properties in the treatment of shale and clay in hydrocarbon recovery; see also Engelmann et at in U.S. Pat. No. 5,196,401.
Other compositions comprising a cationic polymer and an anionic surfactant, often in high ratios of anionic surfactant to cationic polymer, may be found in Matz and LeMar U.S. Pat. No. 6,110,451, Verdicchio and Spilatro U.S. Pat. No. 4,948,576, and the shampoo and other personal care products described by Guskey et at in U.S. Pat. No. 6,297,203 and 6,221,817, Sako et at in U.S. Pat. No. 6,284,230, (which also describes betaines) Hoshowski et at in U.S. Pat. No. 5,137,715, and Snyder et at in U.S. Pat. No. 6,248,317.
In the field of hydrocarbon recovery from the earth, formation fracturing fluids proposed by Zhang in Canadian patent 2,257,699 combine anionic surfactants such as sodium xylene sulfonate and cationic surfactants such as N,N,N, trimethyl-1-octadecammonium chloride to make a gel said to be viscoelastic. Carbon dioxide is added to similar combinations in Zhang's Canadian patent 2,257,697 to generate a foam. Borchardt et at, in U.S. Pat. No. 4,409,110, describe formation flooding compositions which may comprise cationic polymers and anionic surfactants. Numerous combinations of surfactants and other compounds are proposed by Dahayanake et at in U.S. Pat. No. 6,258,859 (WO 98/56497; PCT/US/12067). See also the compositions said to be viscoelastic and proposed for well treatment by Hughes et at in U.S. Pat. No. 6,232,274 and Jones et at in U.S. Pat. No. 6,194,356.
Combinations of cationic polymers, betaines, and anionic surfactants may be inferred from the numerous combinations of materials that are possibly viscoelastic within the disclosure of Balzer in U.S. Pat. No. 5,956,502, dealing with compositions for use on the hair and skin. See also the combination of cationic polymer with anionic surfactants for use as an automatic dishwashing detergent, in Tartakovsky et al U.S. Pat. No. 6,281,180.
Mechanical devices known as pigs have been used to separate moving fluids in pipes. See, for example, Ross's U.S. Pat. No. 6,332,930. Byrd et al, in U.S. Pat. No. 4,767,603, describes the use of pigs: “In a fluid conducting system, articles referred to as ‘pigs’ are used to separate fluids moving through the system. For example, in a continuous polymer reactor system . . . pigs are used to separate different volumes of polymers that are moved through the tubing . . . en route to being injected into a well during a tertiary hydrocarbon recovery operation . . . . The general purpose of a pig used in a fluid conducting system is to provide a movable fluid-sealing barrier between the fluids.” Column 1, lines 13–31. Pigs and plugs made of various gels are disclosed in the following US patents, as examples: Onan et al U.S. Pat. Nos. 5,346,011 and 5,483,986, Purinton U.S. Pat. Nos. 4,537,700, 4,543,131 and 4,473,408, Bradley U.S. Pat. No. 6,076,278, Himes U.S. Pat. No. 5,346,339, and Broussard et al U.S. Pat. No. 4,252,456. Specific uses include pipeline cleaning, pipeline drying, separation of cementing compositions in well treatment, and others.
There remains a need for improved aqueous gel plugs and pigs; there is a particular need for a versatile gel suitable for a wide range of such uses.